The present invention relates to a small-size motor and, more particularly, to a small-size motor in which the characteristics of a brush unit are improved.
FIG. 7 shows a brush unit for a conventional small-size motor. Usually, the small-size motor is configured by containing a rotor composed by assembling various parts on a shaft, together with magnets serving as magnetic poles on a stator, in a motor case and by mounting a case cover on an opening of the motor case. Also, the case cover is usually provided with brushes and their electrical and mechanical connecting arrangement. FIG. 7 is a view of the case cover, which is viewed from a motor inside.
Each brush unit is made up of a carbon brush 1, a brush arm 2, and a brush base 3. In this conventional brush unit, the brush arm 2 is bent into an L shape, and is fixed to the brush base 3 in a fixing portion 7. Each attachment groove is formed between protruding portions formed integrally with the case cover made of a synthetic resin so as to hold and support only one location of the fixing portion in which the brush arm 2 is fixed to the brush base 3. End portions of the brush bases 3, which function as receptacle terminals 5, come into contact with a pair of outside terminals 24 inserted from the outside through outside terminal insertion holes 10.
However, it has been revealed from a result of structural analysis that in the conventional bush device, since the brush arm 2 is bent into an L shape, noise is generated by an occurrence of a vibration component in an axial direction of the motor at a brush sliding portion at which the carbon brush 1 slides with respect to a commutator at the time of motor rotation.
Further, the outside terminal 24 is inserted through the outside terminal insertion hole 10 and presses on the receptacle terminal 5 (brush base 3), so that this influence reaches the brush sliding portion, whereby the brush tension may be undesirably changed.
Also, the end portion (contact portion contacting with the outside terminal 24) of the receptacle terminal 5 must be set at a position near the outside terminal insertion hole 10 in order that the receptacle terminal 5 may be used for a short outside terminal 24, which presents a problem in that the receptacle terminal 5 cannot be lengthened. A short receptacle terminal 5 cannot ensure sufficiently high spring properties.
The present invention has been achieved to solve the above problems, and accordingly an object thereof is to provide a small-size motor having brush units in which a brush arm need not be bent into an L shape and noise can be reduced by decreasing a vibration component in the axial direction of the motor at a sliding portion at which a carbon brush slides with respect to a commutator at the time of motor rotation.
Also, another object of the present invention is to provide a small-size motor having brush units in which brush tension is not changed when outside terminals are inserted through outside terminal insertion holes.
Further, still another object of the present invention is to provide a small-size motor having brush units capable of being used for short outside terminals.
The small-size motor in accordance with the present invention includes: a metallic case 21 of a bottomed hollow cylindrical shape, fitted with magnets 22 on the inner peripheral surface thereof; a case cover 4 made of a synthetic resin, mounted so as to close an opening of the case 21 and fitted with brush units; a rotor fitted with a laminated core 16; windings 17 wound on the laminated core 16; and a commutator 14 on a shaft 15. The brush unit includes: a carbon brush 1 being into slidable contact with the commutator 14; a substantially straight brush arm 2 for holding the carbon brush 1; and a brush base 3 connected to the brush arm 2. The brush base 3 is provided with a receptacle terminal 5 formed by cutting and raising the brush base 3, and thereby the brush base 3 is formed with a base hole 6 corresponding to the receptacle terminal 5. The case cover 4 is formed with outside terminal insertion holes 10 for inserting terminals for electrical connection from the outside to bring the terminals into contact with the receptacle terminals 5. The brush unit is installed to the case cover 4 at two locations of a fixing portion 8 in which the brush arm 2 is fixed to the brush base 3, and a brush base end portion 9 integral with a base portion 5xe2x80x2 of the receptacle terminal 5.
Also, the present invention provides a small-size motor in which a brush base 3 is formed with a base hole 6 in the center thereof, a male terminal 11 for electrical connection from the outside is provided at one end of the brush base 3, and a case cover 4 is formed with openings (male terminal projecting holes 12) for projecting the male terminals 11. In this small-size motor, likewise, a brush unit is installed to the case cover 4 at two locations of a fixing portion in which a brush arm 2 is fixed to the brush base 3, and a brush base end portion.